let b1 = new Uint8Array(1);
let b2 = new Uint8ClampedArray(1);
console.log(b1[0]); // 0
console.log(b2[0]); // 0
// b1[0] 将发生溢出
b1[0] = 257;
// b2[0] 会固定在 0 ~ 255，超过该范围取最近的极值
b2[0] = 257;
console.log(b1[0]); // 1
console.log(b2[0]); // 255
